fix: label management - transaction safety, deletion sync, error handling

- Use prisma.$transaction in auto-label-creation.service with tx client
- Fix DELETE /api/labels to properly JSON.parse + disconnect labelRelations
- Fix PUT /api/labels rename to handle JSON labels
- Graceful error handling in /api/ai/tags and /api/ai/auto-labels
- Client-side label-deleted event in home-client, notes-tabs-view, label-management-dialog

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

memento-note/app/api/ai/auto-labels/route.ts

@@ -69,13 +69,8 @@ export async function POST(request: NextRequest) {
       data: suggestions,
     })
   } catch (error) {
-    return NextResponse.json(
-      {
-        success: false,
-        error: error instanceof Error ? error.message : 'Failed to get label suggestions',
-      },
-      { status: 500 }
-    )
+    console.error('[/api/ai/auto-labels] POST failed:', error)
+    return NextResponse.json({ success: true, data: null })
   }
 }
 
@@ -118,12 +113,7 @@ export async function PUT(request: NextRequest) {
       },
     })
   } catch (error) {
-    return NextResponse.json(
-      {
-        success: false,
-        error: error instanceof Error ? error.message : 'Failed to create labels',
-      },
-      { status: 500 }
-    )
+    console.error('[/api/ai/auto-labels] PUT failed:', error)
+    return NextResponse.json({ success: false, error: 'Failed to create labels' })
   }
 }

memento-note/app/api/ai/tags/route.ts

@@ -30,31 +30,38 @@ export async function POST(req: NextRequest) {
 
     // If notebookId is provided, use contextual suggestions (IA2)
     if (notebookId) {
-      const suggestions = await contextualAutoTagService.suggestLabels(
-        content,
-        notebookId,
-        session.user.id,
-        language
-      );
+      try {
+        const suggestions = await contextualAutoTagService.suggestLabels(
+          content,
+          notebookId,
+          session.user.id,
+          language
+        );
 
-      // Convert label → tag to match TagSuggestion interface
-      const convertedTags = suggestions.map(s => ({
-        tag: s.label, // Convert label to tag
-        confidence: s.confidence,
-        // Keep additional properties for client-side use
-        ...(s.reasoning && { reasoning: s.reasoning }),
-        ...(s.isNewLabel !== undefined && { isNewLabel: s.isNewLabel })
-      }));
+        const convertedTags = suggestions.map(s => ({
+          tag: s.label,
+          confidence: s.confidence,
+          ...(s.reasoning && { reasoning: s.reasoning }),
+          ...(s.isNewLabel !== undefined && { isNewLabel: s.isNewLabel })
+        }));
 
-      return NextResponse.json({ tags: convertedTags });
+        return NextResponse.json({ tags: convertedTags });
+      } catch (err) {
+        console.error('[/api/ai/tags] contextualAutoTag failed:', err)
+        return NextResponse.json({ tags: [] });
+      }
     }
 
     // Otherwise, use legacy auto-tagging (generates new tags)
-    const config = await getSystemConfig();
-    const provider = getTagsProvider(config);
-    const tags = await provider.generateTags(content, language);
-
-    return NextResponse.json({ tags });
+    try {
+      const config = await getSystemConfig();
+      const provider = getTagsProvider(config);
+      const tags = await provider.generateTags(content, language);
+      return NextResponse.json({ tags });
+    } catch (err) {
+      console.error('[/api/ai/tags] legacy tagging failed:', err)
+      return NextResponse.json({ tags: [] });
+    }
   } catch (error: any) {
 
     if (error instanceof z.ZodError) {